Work and Power

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Mechanical Energy

Give me a point to lean on and I’ll lift the world up ~ Archimedes (287-212 B.C.)

Mechanical energy, in the form of muscle power, was the first energy source that humans utilized. Hunters used muscle power to chase and wrestle animals or escape them when in danger. The use of tools for hunting and agriculture opened a new era in human development. The bow and arrow was used in hunting and in warfare, and wind was harnessed to navigate sailboats along rivers and on seas. As animals became domesticated, humans learned to exploit animal power - first oxen, then mules and horses - for pulling their plows and carts. The great civilizations of China, Egypt, Persia, Greece, and Rome relied on forced labor and animals to plow their farms; at the same time, their soldiers fought for the acquisition of more land and slaves.

As the empires crumbled and slaves became scarce, the work of humans and animals was increasingly supplemented by power from watermills and windmills. Although the invention of windmills and watermills can be traced back to ancient Persians, Greeks and Romans, their use was limited primarily to grinding grains. They became widespread only at the end of the first millennium when Europeans used mills to operate such tools as saws and looms and to pump water from wells.

The work from muscles, the work performed by windmills and watermills, and the work done by simple tools are all examples of mechanical energy. In this chapter we will define mechanical energy and how it manifests itself in the form of kinetic and potential energies. Hydro and wind energies will be discussed in their respective sections.


(1) Toossi Reza, "Energy and the Environment:Sources, technologies, and impacts", Verve Publishers, 2005

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